[Qemu-devel] [PATCH v2 8/8] migration/ram: ensure write persistence on loading xbzrle pages to PMEM

[Haozhong Zhang <haozhong.zhang@intel.com>]

When loading a xbzrle encoded page to persistent memory, load the data
via libpmem function pmem_memcpy_nodrain() instead of memcpy().
Combined with a call to pmem_drain() at the end of memory loading, we
can guarantee those xbzrle encoded pages are persistently loaded to PMEM.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
---
 migration/ram.c    | 15 ++++++++++-----
 migration/xbzrle.c | 20 ++++++++++++++++++--
 migration/xbzrle.h |  1 +
 3 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 924d2b9537..87f977617d 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2388,10 +2388,10 @@ static void ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
     }
 }
 
-static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
+static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host, bool is_pmem)
 {
     unsigned int xh_len;
-    int xh_flags;
+    int xh_flags, rc;
     uint8_t *loaded_data;
 
     /* extract RLE header */
@@ -2413,8 +2413,13 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
     qemu_get_buffer_in_place(f, &loaded_data, xh_len);
 
     /* decode RLE */
-    if (xbzrle_decode_buffer(loaded_data, xh_len, host,
-                             TARGET_PAGE_SIZE) == -1) {
+    if (!is_pmem) {
+        rc = xbzrle_decode_buffer(loaded_data, xh_len, host, TARGET_PAGE_SIZE);
+    } else {
+        rc = xbzrle_decode_buffer_to_pmem(loaded_data, xh_len, host,
+                                          TARGET_PAGE_SIZE);
+    }
+    if (rc == -1) {
         error_report("Failed to load XBZRLE page - decode error!");
         return -1;
     }
@@ -2974,7 +2979,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
             break;
 
         case RAM_SAVE_FLAG_XBZRLE:
-            if (load_xbzrle(f, addr, host) < 0) {
+            if (load_xbzrle(f, addr, host, is_pmem) < 0) {
                 error_report("Failed to decompress XBZRLE page at "
                              RAM_ADDR_FMT, addr);
                 ret = -EINVAL;
diff --git a/migration/xbzrle.c b/migration/xbzrle.c
index 1ba482ded9..499d8e1bfb 100644
--- a/migration/xbzrle.c
+++ b/migration/xbzrle.c
@@ -12,6 +12,7 @@
  */
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
+#include "qemu/pmem.h"
 #include "xbzrle.h"
 
 /*
@@ -126,7 +127,8 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
     return d;
 }
 
-int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
+static int xbzrle_decode_buffer_common(uint8_t *src, int slen, uint8_t *dst,
+                                       int dlen, bool is_pmem)
 {
     int i = 0, d = 0;
     int ret;
@@ -167,10 +169,24 @@ int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
             return -1;
         }
 
-        memcpy(dst + d, src + i, count);
+        if (!is_pmem) {
+            memcpy(dst + d, src + i, count);
+        } else {
+            pmem_memcpy_nodrain(dst + d, src + i, count);
+        }
         d += count;
         i += count;
     }
 
     return d;
 }
+
+int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
+{
+    return xbzrle_decode_buffer_common(src, slen, dst, dlen, false);
+}
+
+int xbzrle_decode_buffer_to_pmem(uint8_t *src, int slen, uint8_t *dst, int dlen)
+{
+    return xbzrle_decode_buffer_common(src, slen, dst, dlen, true);
+}
diff --git a/migration/xbzrle.h b/migration/xbzrle.h
index a0db507b9c..ac5ae32666 100644
--- a/migration/xbzrle.h
+++ b/migration/xbzrle.h
@@ -18,4 +18,5 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
                          uint8_t *dst, int dlen);
 
 int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);
+int xbzrle_decode_buffer_to_pmem(uint8_t *src, int slen, uint8_t *dst, int dlen);
 #endif
-- 
2.14.1